How does the over voltage surge affect the power system?

How does the over voltage surge affect the power system?
by

1 Answer

Answer :

The over voltage of the power system leads to insulation breakdown of the equipments. It causes the line insulation to flash over and may also damage the nearby transformer, generators and the other equipment connected to the line.
by

Related questions

What is the difference between surge arrestor and lightning arrestor?

Description : What is the difference between surge arrestor and lightning arrestor?

Last Answer : Lightning arrestor is installed outside and the effect of lightning is grounded, whereas surge arrestor installed inside panels comprising of resistors which consumes the energy and nullify the effect of surge.

When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?

Description : When voltage increases then current also increases then what is the need of over voltage relay and over current relay? Can we measure over voltage and over current by measuring current only?

Last Answer : No. We can't sense the over voltage by just measuring the current only because the current increases not only for over voltages but also for under voltage (As most of the loads are non-linear in ... So, for a better protection of the system. It should have both over voltage & over current relay.

What are the various faults that would affect an alternator?

Description : What are the various faults that would affect an alternator?

Last Answer : (a) Stator faults 1, Phase to phase faults 2, Phase to earth faults 3, Inter turn faults (b) 1, Earth faults 2, Fault between turns 3, Loss of excitation due to fuel failure (c) 1, Over ... rise, resulting in shattering of the turbine low pressure casing (d) 1, Fault on lines 2, Fault on busbars

What is meant by knee point voltage?

Description : What is meant by knee point voltage?

Last Answer : Knee point voltage is the voltage at which a CT gets saturated. It is one of the important factors taken into consideration for selecting a current transformer.

What is meant by recovery voltage?

Description : What is meant by recovery voltage?

Last Answer : The power frequency rms voltage appearing across the breaker contacts after the arc is extinguished and transient oscillations die out is called recovery voltage.

What is restriking voltage?

Description : What is restriking voltage?

Last Answer : It is the transient voltage appearing across the breaker contacts at the instant of arc being extinguished.

What is reverse power relay?

Description : What is reverse power relay?

Last Answer : Reverse Power flow relay are used to stop the flow of power from grid to station generator when the generating units are off.

What is power swing?

Description : What is power swing?

Last Answer : During switching of lines or wrong synchronization surges of real and reactive power flowing in transmission line causes severe oscillations in the voltage and current vectors. It is represented by curves originating in load regions and traveling towards relay characteristics.

What are the problems arising in differential protection in power transformer and how are they overcome?

Description : What are the problems arising in differential protection in power transformer and how are they overcome?

Last Answer : 1. Difference in lengths of pilot wires on either sides of the relay. This is overcome by connecting adjustable resistors to pilot wires to get equipotential points on the pilot wires. 2. ... harmonic restraining unit is added to the relay which will block it when the transformer is energized.

Define the term pilot with reference to power line protection.

Description : Define the term pilot with reference to power line protection.

Last Answer : Pilot wires refers to the wires that connect the CT’s placed at the ends of a power transmission line as part of its protection scheme. The resistance of the pilot wires is usually less than 500 ohms.

Mention the short comings of Merz Price scheme of protection applied to a power transformer.

Description : Mention the short comings of Merz Price scheme of protection applied to a power transformer.

Last Answer : In a power transformer, currents in the primary and secondary are to be compared. As these two currents are usually different, the use of identical transformers will give differential current, and ... turn-ratio are used, the differential current may flow through the relay under normal condition.

Mention some of the applications of Directional Over-Current relays?

Description : Mention some of the applications of Directional Over-Current relays?

Last Answer : 1. Double end fed power system 2. Single end fed system of parallel feeders 3. Ring main feeder system

What are the advantages of air blast circuit breaker over oil circuit breaker?

Description : What are the advantages of air blast circuit breaker over oil circuit breaker?

Last Answer : o The risk of fire is diminished o The arcing time is very small due to rapid buildup of dielectric strength between contacts o The arcing products are completely removed by the blast whereas oil deteriorates with successive operations

What are the disadvantages of MOCB over a bulk oil circuit breaker?

Description : What are the disadvantages of MOCB over a bulk oil circuit breaker?

Last Answer : o The degree of carbonization is increased due to smaller quantity of oil o There is difficulty of removing the gases from the contact space in time o The dielectric strength of the oil deteriorates rapidly due to high degree of carbonization.

What are the advantages of MOCB over a bulk oil circuit breaker?

Description : What are the advantages of MOCB over a bulk oil circuit breaker?

Last Answer : • It requires lesser quantity of oil • It requires smaller space • There is a reduced risk of fire • Maintenance problem are reduced

What are the advantages of static relay over electromagnetic relay?

Description : What are the advantages of static relay over electromagnetic relay?

Last Answer : o Low power consumption as low as 1mW o No moving contacts; hence associated problems of arcing, contact bounce, erosion, replacement of contacts o No gravity effect on operation of ... testing and servicing. Can convert even non-electrical quantities to electrical in conjunction with transducers.

What is over fluxing protection in transformer?

Description : What is over fluxing protection in transformer?

Last Answer : If the turns ratio of the transformer is more than 1:1, there will be higher core loss and the capability of the transformer to withstand this is limited to a few minutes only. This phenomenon is called over fluxing.

What are the causes of over speed and how alternators are protected from it?

Description : What are the causes of over speed and how alternators are protected from it?

Last Answer : Sudden loss of all or major part of the load causes over-speeding in alternators. Modern alternators are provided with mechanical centrifugal devices mounted on their driving shafts to trip the main valve of the prime mover when a dangerous over-speed occurs.

What are over and under current relays?

Description : What are over and under current relays?

Last Answer : Overcurrent relays are those that operate when the current in a line exceeds a predetermined value. (eg: Induction type non-directional/directional overcurrent relay, differential overcurrent relay)whereas ... in a circuit/line drops below a predetermined value.(eg: differential over-voltage relay)

Name the different kinds of over current relays.

Description : Name the different kinds of over current relays.

Last Answer : Induction type non-directional over current relay, Induction type directional over current relay & current differential relay.

What is different between resistance grounding system and resistance earthing system?

Description : What is different between resistance grounding system and resistance earthing system?

Last Answer : In resistance grounding system the neutral point of the load is connected to the ground to carry the residual current in case of unbalanced conditions. Resistance earthing system is done in an electric equipment in order to protect the equipment in occurrence of fault in the system.

What are unit system and non unit system?

Description : What are unit system and non unit system?

Last Answer : A unit protective system is one in which only faults occurring within its protected zone are isolated. Faults occurring elsewhere in the system have no influence on the operation of a unit system. ... is a protective system which is activated even when the faults are external to its protected zone.

In three pin plug why earth pin diameter is higher than other two pin?

Description : In three pin plug why earth pin diameter is higher than other two pin?

Last Answer : Because Current flow in the conductor is inversely proportional to the conductor diameter. So if any short circuits occur in the system first high currents bypassed in the Earthling terminal. (R=Pl/a area of the conductor increases resistance value decreases)

Where are the lighting arrestors placed in distribution lines?

Description : Where are the lighting arrestors placed in distribution lines?

Last Answer : Near distribution transformers and outgoing feeders of 11kv and incoming feeder of 33kv and near power transformers in sub-stations.

What is the difference between megger test equipment and contact resistance meter test instruments?

Description : What is the difference between megger test equipment and contact resistance meter test instruments?

Last Answer : Megger test equipment used to measure cable electric resistance, conductor continuity, phase identification. Contact resistance meter test instruments used to measure low resistance like relays, contactors.

what is Buchholz relay and the significance of it in to the transformer?

Description : what is Buchholz relay and the significance of it in to the transformer?

Last Answer : Buchholz relay is a device which is used for the protection of transformer from its internal faults, it is a gas based relay. whenever any internal fault occurs in a transformer, the Buchholz ... circuit then it stop its sound itself otherwise it trips the circuit by its own tripping mechanism.

What is inrush current?

Description : What is inrush current?

Last Answer : the initial value of flux is zero when the transformer is energized. The, the flux reaches a peak value in half a cycle. Since power transformers operate near the knee of the saturation curve, a flux ... the order of 8 to 30 times the full-load current. This current is known as inrush current.

What are the different types of faults in a transformer?

Description : What are the different types of faults in a transformer?

Last Answer : The internal faults include phase faults, ground faults, inter-turn faults, tap-changer failure, and leakage oil from tank. The external faults include system phase faults, system ground faults, over loads and over fluxing.

Explain differential protection?

Description : Explain differential protection?

Last Answer : Differential protection is based on the fact that any fault within an electrical equipment would cause the current entering it, to be different, from that leaving it. Thus, we can compare the two ... phase or both and issue a trip output if the difference exceeds a pre- determined set value.

What is dielectric test of a circuit breaker?

Description : What is dielectric test of a circuit breaker?

Last Answer : It consists of overvoltage withstand test of power frequency lightning and impulse voltages.Testa are done for both internal and external insulation with switch in both open and closed conditions.

How direct tests are conducted in circuit breakers?

Description : How direct tests are conducted in circuit breakers?

Last Answer : Using a short circuit generator as the source. Using the power utility system or network as the source.

Differentiate between a fuse and a circuit breaker.

Description : Differentiate between a fuse and a circuit breaker.

Last Answer : Fuse is a low current interrupting device. It is a copper or an aluminium wire. Circuit breaker is a high current interrupting device and it act as a switch under normal operating conditions.

Define single line diagram.

Description : Define single line diagram.

Last Answer : Representation of various power system components in a single line is defined as single line diagram.

Mention the inductance value of the peterson’s coil.

Description : Mention the inductance value of the peterson’s coil.

Last Answer : L=1/3wc2

State the different types of circuit breakers.

Description : State the different types of circuit breakers.

Last Answer : Air ,oil,vacuum circuit breakers.

Mention the withstanding current in our human body.

Description : Mention the withstanding current in our human body.

Last Answer : 9mA

State the various types of unsymmetrical faults.

Description : State the various types of unsymmetrical faults.

Last Answer : Line to ground ,line to line and double line to ground faults

State the different types of faults.

Description : State the different types of faults.

Last Answer : Symmetrical faults and unsymmetrical faults and open conductor faults.

Define negative sequence component.

Description : Define negative sequence component.

Last Answer : It has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and has the phase sequence in opposite to its original phasors.

State the significance of double line fault.

Description : State the significance of double line fault.

Last Answer : It has no zero sequence component and the positive and negative sequence networks are connected in parallel.

Define zero sequence component.

Description : Define zero sequence component.

Last Answer : They has 3 vectors having equal magnitudes and displaced from each other by an angle zero degrees.

Define positive sequence component.

Description : Define positive sequence component.

Last Answer : -has 3 vectors equal in magnitude and displaced from each other by an angle 120 degrees and having the phase sequence as original vectors.

State the three sequence components.

Description : State the three sequence components.

Last Answer : Positive sequence components, negative sequence components and zero sequence components.

What are symmetrical components?

Description : What are symmetrical components?

Last Answer : It is a mathematical tool to resolve unbalanced components into balanced components.

State the significance of single line to ground fault.

Description : State the significance of single line to ground fault.

Last Answer : In single line to ground fault all the sequence networks are connected in series. All the sequence currents are equal and the fault current magnitude is three times its sequence currents.

What is arc suppression coil?

Description : What is arc suppression coil?

Last Answer : A method of reactance grounding used to suppress the arc due to arcing grounds.

What are arcing grounds?

Description : What are arcing grounds?

Last Answer : The presence of inductive and capacitive currents in the isolated neutral system leads to formation of arcs called as arcing grounds.

State the various types of earthing.

Description : State the various types of earthing.

Last Answer : Solid earthing, resistance earthing , reactance earthing , voltage transformer earthing and zig-zag transformer earthing.

Define composite testing of a circuit breaker.

Description : Define composite testing of a circuit breaker.

Last Answer : In this method the breaker is first tested for its rated breaking capacity at a reduced voltage and afterwards for rated voltage at a low current.This method does not give a proper estimate of the breaker performance.

State the disadvantages of field tests.

Description : State the disadvantages of field tests.

Last Answer : The circuit breaker can be tested at only a given rated voltage and network capacity. The necessity to interrupt the normal services and to test only at light load conditions. Extra inconvenience and expenses in installation of controlling and measuring equipment in the field.